A photographic material has been hitherto researched to make it possible to carry out contact exposure work (so-called contact work step) with a photographic light-sensitive material having a relatively low sensitivity in a bright room when manufacturing printing plate. A photographic light-sensitive material which can be handled in an area generally referred to as a bright room while using silver halide as the light-sensitive element has recently been developed. This is attained by exposing a light-sensitive material having an extremely low sensitivity (e.g., about 1/10.sup.4 which is the sensitivity of an ordinary silver halide photographic material) with respect to visible light to a light source containing a large amount of ultraviolet rays under a safety light which substantially emits no ultraviolet rays.
On the other hand, a so-called contact work of reproduction process is performed by not only a simple one-sheet contact reproduction work (i.e., a step of performing a nega-posi transformation by contact-exposing reproduction film for contact work using one-sheet of developed film as the original, and developing the light-sensitive silver halide material), but also advanced image transformation referred to a "image-letter superimposition".
The image-letter superimposition means a step conducted in contact work for making non-inked portion of a letter, symbol, etc. (called "letter image"), existing in a print at the portion of ink dots on paper (dot-image portion) and the wholly inked portion (called "solid black" portion). The image-letter superimposition during a photomechanical process is more practically explained by referring to the accompanying drawing. That is, as shown in the FIGURE, a superimposed assembly of a developed dot-image-formed film (dot-image original) 4 attached to a transparent or translucent film base (usually, a polyethylene terephthalate film of several hundreds .mu.m in thickness is used) 3 and a developed film 2 having formed thereon a so-called line positive image of a letter or a symbol (line image original) attached to a base film 1 similar to the base film 3 is used as an original. The silver halide emulsion layer of a reproduction light-sensitive film 5 for contact work is brought into contact with the dot-image portion of the original. The reproduction film is light-exposed and developed to form a clear portion of the line image in the dot-images. The important point in the process is that the dot-image and the line image must perform nega-posi transformation according to the dot area and the line width, respectively.
For example, a dot-image having a black area of 50% must be accurately transformed into a white area of 50% and a line image having a black line width of 50 .mu.m must be transformed into a white line having a width of 50 .mu.m. However, as is clear from the FIGURE, while dot-image is exposed on a reproduction film for contact work in a direct contact state with the silver halide emulsion layer of the reproduction film, a line image is exposed on a reproduction film for contact work through the dot-image original 4 (usually having a thickness of about 110 .mu.m) and the base 3 (having a thickness of several hundreds .mu.m) for attaching thereto the dot-image original. More specifically, the line image is exposed on the reproduction film for contact work as a dimmed or indistinct image through a transparent or translucent spacer having several hundred .mu.m thickness. Accordingly, if an ordinary exposure amount (i.e., the exposure amount capable of faithfully performing a nega-posi transformation of dot area) is applied, the clear line width of the line image is narrowed by the influence of the dimmed exposure. On the other hand, if the exposure amount is reduced in order to reduce the influence of the dimmed exposure and perform a faithful nega-posi transformation of the line width of a line image, the dot area becomes narrow due to deficient exposure. This phenomenon is largely influenced not only by a light-sensitive material but also by the exposure light source. That is, if the size of a light source for exposure is as small as a point light source, the extent of the foregoing dimmed exposure can be reduced. However, since an exposure means capable of providing a large amount of exposure must be used when using a light-sensitive material for a bright room, the light source is larger than that of a conventional dark room-type exposure means. This causes deterioration in the quality of the latter image.
There has been substantially no published information with respect to a means for eliminating the deterioration of the quality of the letter image.
Emulsions of silver halide light-sensitive materials which can be handled in a bright room which have therein silver halide grains formed by the addition of a large amount of a rhodium salt are described in, for example, Japanese patent application (OPI) Nos. 125734/81, 149030/81 and 149031/81 (the term "OPI" as used herein refers to a "published unexamined Japanese patent appplication"). However, no techniques for improving the quality of the letter image are described in these specifications of these patent applications. The foregoing patent applications also disclose the addition of polyalkylene oxides to developers. The results of comparison sample I described in Example 1 of the present invention which will be described later in this specification clearly show that the mere addition of a polyalkylene oxide to a developer does not improve the quality of the letter image.
A number of recent attempts have been made to obtain image quality equal to lithographic development by quick and stable processing. There has also been an increase in demand for performing the image-letter superimposition which is a higher image transformation work by similar quick and stable processing. However, no practical techniques for meeting the demand have been developed.